GENERAL HISTOLOGY

Detailed explanation-1: -Glucose and amino acids are reabsorbed by Na+-coupled transport in the proximal tubule (see Fig. 11-10A). A family of transport proteins on the apical surface of the epithelial cell uses the diffusion of Na+ down its electrochemical gradient as the energy source.

Detailed explanation-2: -Firstly, the glucose in the proximal tubule is co-transported with sodium ions into the proximal convoluted tubule walls via the SGLT2 cotransporter. Some (typically smaller) amino acids are also transported in this way.

Detailed explanation-3: -The proximal convoluted tubule (PCT) uses both cellular and paracellular transport mechanisms. The apical membrane has an expanded surface area available for reabsorption and tight junctions enabling high-capacity fluid reabsorption.

Detailed explanation-4: -Active transport is the key to the reabsorptive processes in the proximal tubule. Glucose and amino acids are reabsorbed across the apical membrane of the proximal tubule by sodium-coupled secondary active transport.

Detailed explanation-5: -Cotransport-this process is particularly important for the reabsorption of water. Water can follow other molecules that are actively transported, particularly glucose and sodium ions in the nephron.